Control of fluid flow is important in many applications, whether the fluid flow be liquid or gas. A common flow control is a check valve, which allows fluid flow in one direction through the valve and prevents reverse flow in the opposite direction.
One commonly encountered fluid control is the so-called Y-pattern valve. These valves are known as Y-pattern valves because the passages through the valve intersect in a pattern resembling the letter Y. For example, an inlet passage can extend into the body of the valve along one direction, an outlet passage can extend in the body along another direction and an intermediate passage along a third direction, forming a Y-pattern where they intersect. The intermediate passage forms the intersection between the inlet and outlet passages. Commonly, some type of valve closure element will be positioned in the intermediate passage for controlling flow between the inlet and outlet passages.
One common Y-pattern valve includes a body defining a narrow annular seal seat along the intermediate passage. The narrow seat lies in a plane generally perpendicular to the flow direction and forms a seat for engagement with an annular valve stem to block flow through the valve. The valve stem is typically threaded into the valve body so that rotation of the valve stem moves the stem toward or away from the narrow annular seat to open and close the valve. While these type of on-off valves are very useful, it would be desirable to use the basic pattern of the valve body for other flow control applications. However, the narrow annular seat found in the valve body has until this time generally only been usable with a conventional valve stem for the limited function of an on/off valve.